Hi everyone.
Few people asked me to help them with reCaptcha on the old but still good MemHT 4.0.2.
You can find the mod here: Download MOD
To make it work, add your site and secret keys in inc_header_custom.php
This mod enables the reCaptcha 2 in the contact and user registration addons.
PS: The mods are marked with a //RECAPTCHA inline comment
Bye!